Adhesive comprising cured amino resin powder for printed circuit board

ABSTRACT

There are disclosed an adhesive obtained by dispersing a cured amino resin fine powder soluble in acid or oxidizing agent into an uncured heat-resistant resin matrix hardly soluble in acid or oxidizing agent when being subjected to a curing treatment as well as a printed circuit board using this adhesive and a method of producing the same. The adhesive has excellent properties such as resistance to chemicals, heat resistance, electric properties, hardness and adhesion property owing to the use of the amino resin fine powder. Therefore, the printed circuit board using such an adhesive is not influenced by service circumstance and is high in the connection reliability without forming short circuit between patterns. Furthermore, in the method of producing the printed circuit board, the adhesive is provided in form of a sheet-or a prepreg, whereby the printed circuit board can be produced easily and cheaply.

This application is a division, of application Ser. No. 07/913,935,filed Jul. 17, 1992, now U.S. Pat. No. 5,344,893.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an adhesive for printed circuit board, amethod of producing a printed circuit board by using the same and aprinted circuit board, and more particularly to an adhesive havingimproved resistance to chemicals, heat resistance, electrical propertiesand adhesion property, a method of easily producing a printed circuitboard by using such an adhesive and a printed circuit board having ahigh reliability.

2. Disclosure of the Related Art

Recently, high densification or high speed access of calculatingfunction in electronic equipments such as large-size computer or thelike is advanced with the progress of electronic technique. As a result,high densification and high reliability through line pattern are latelyrequired even in printed circuit board and LSI mounted print circuitboard. Particularly, multilayer printed circuit boards having aplurality of printed circuit layers are lately spotlighted in accordancewith high densification and high-speed access.

In the production of the printed circuit board, there has hitherto beenknown a so-called etched foil method in which a copper foil is laminatedonto a substrate and subjected to a photoetching to form a conductorcircuit as a method for the formation of conductor circuit. According tothis method, the conductor circuit having an excellent adhesion propertyto the substrate can be formed, but there is a serious drawback that itis difficult to obtain a fine pattern of a high accuracy by etchingbecause the thickness of the copper foil is thick. Furthermore, theproduction steps become complicated and also the production efficiencyis poor.

As a method of forming the conductor circuit onto the substrate,therefore, there has recently been adopted a so-called additive methodwherein an adhesive including a diene series synthetic rubber is appliedto the surface of the substrate to form an adhesive layer and then thesurface of the adhesive layer is toughened and subjected to anelectroless plating to form a conductor circuit.

However, the adhesive usually used in the latter method includes thesynthetic rubber, so that the heat resistance is low because theadhesion strength is largely lowered at, for example, high temperatureand the electroless plated film swells during the soldering, and theelectric properties such as surface resistivity and the like areinsufficient, and hence the use range is fairly restricted.

As a typical example of the multilayer printed circuit board, there is asystem that plural circuit plates each provided with an internal circuitpattern are laminated with each other through a prepreg as an insulatinglayer and pressed and then a through-hole is formed therein to connectand electrically conduct the internal circuit patterns to each other.

In the multilayer printed circuit board this system, the plural internalcircuit patterns are connected and electrically conducted to each otherthrough the through-hole, and the wiring circuit pattern becomes toocomplicated, so that it is difficult to realize the high densificationor high speed access.

For this end, there are lately developed multilayer printed circuitboards, in which conductor circuit and organic insulating films arealternately built up on each other, as a multilayer printed circuitboard capable of overcoming the above problem. Such a multilayer printedcircuit board is certainly suitable for extra-high densification andhigh speed access.

However, it is actually difficult to form an electroless plated film onthe organic insulating layer with a good reliability. In the multilayerprinted circuit board, therefore, the conductor circuit is formed by PVDprocess such as vapor deposition, sputtering and the like, or by usingelectroless plating with the above PVD process. However, the formationof conductor circuit through PVD process is poor in the productivity andundesirably high in the cost.

On the other hand, the inventors have made various studies in order tosolve the aforementioned problems produced in the above adhesives forelectroless plating, and previously proposed an adhesive for electrolessplating having improved heat resistance, electrical properties andadhesion property to the electroless plated film and capable ofrelatively easily utilizing it and a method of producing circuit boardsby using the adhesive and printed circuit boards produced therefrom(Japanese Patent laid open No. 61-276875, No. 63-126297, No. 2-182731,No. 2-88992, and U.S. Pat. Nos. 4,752,499, 5,021,472 and 5,055,321).

That is, these techniques relate to an adhesive in which heat-resistantresin powder being soluble in an oxidizing agent and subjected to acuring treatment is dispersed into an uncured heat-resistant resinmatrix being insoluble in the oxidizing agent through the curingtreatment, and a method of producing printed circuit boards in which theabove adhesive is applied to a substrate and dried and cured to form anadhesive layer, and thereafter at least a part of the above powderdispersed in the surface portion of the adhesive layer is dissolved andremoved to roughen the surface of the adhesive layer, and then the thustreated substrate is subjected to an electroless plating as well asprinted circuit boards produced by this method.

In the adhesive according to these techniques, the fine powder of thepreviously cured epoxy resin is dispersed into the heat-resistant resinmatrix, so that when the adhesive is applied to the substrate and thendried and cured, the heat-resistant resin fine powder is at a uniformlydispersed state in the heat resistant resin forming the matrix. Sincethere is a difference in the solubility in the oxidizing agent betweenthe heat-resistant resin fine powder and the heat-resistant resinmatrix, the fine powder dispersed in the surface of the adhesive layeris mainly dissolved and removed by treating the adhesive layer with theoxidizing agent to effectively form an anchor recess, whereby thesurface of the adhesive layer can be toughened uniformly and hence thehigh adhesion strength and high reliability to the electroless platedfilm can be obtained.

In the above adhesive, easily available epoxy resins having excellentresistance to chemicals, heat resistance, electrical properties andhardness are used as the cured heat-resistant resin fine powder solublein acid or oxidizing agent.

However, it has been confirmed that when the printed circuit boardproduced by using epoxy resin as a heat-resistant resin fine powder isused in an atmosphere of high temperature and humidity, dissolution andprecipitation of copper forming the wiring circuit pattern are caused tolower the value of surface resistivity and hence a short circuit isformed between the patterns with the rapid advance of high densificationin the printed circuit board.

This happens because, an ionic compound is used in the production ofepoxy resin powder soluble in acid or oxidizing agent, so that sodiumion or chlorine ion remains in the epoxy resin fine powder and causesmigration reaction as shown in the following reaction formulae (1)-(3)(see FIG. 5):

    Na.sup.+ +Cl.sup.- +H.sub.2 O→NaOH+Hcl              (1)

    Cu+2NaOH→Cu(OH).sub.2 +2Na.sup.+                    ( 2)

    Cu+2HCl→CuCl.sub.2 +2H.sup.+                        ( 3)

Thus, in the conventional printed circuit boards, there is still aproblem that the reliability is lowered in accordance with the usecondition due to the use of the epoxy resin inevitably containing sodiumion and chlorine ion.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an adhesive having excellentresistance to chemicals, heat resistance, electrical properties,hardness and adhesion property.

It is another object of the invention to easily and cheaply produce aprinted circuit board by using the above adhesive in form of a sheet, aprepreg or the like.

It is the other object of the invention to provide a printed circuitboard having a high connecting reliability without forming short circuitbetween wiring circuit patterns.

The inventors have made various studies with respect to resins using noionic compound in order to achieve the above objects, and found thatadhesives for circuit boards having excellent resistance to chemicals,heat resistance, electrical properties and hardness are obtained withoutcausing the above reactions by using amino resins as a heat-resistantresin fine powder soluble in an acid or an oxidizing agent.

According to a first aspect of the invention, there is the provision ofan adhesive for printed circuit boards comprising an uncuredheat-resistant resin matrix being insoluble in an acid or an oxidizingagent when being subjected to a curing treatment, and a cured finepowder of amino resin soluble in an acid or an oxidizing agent anddispersed thereinto.

As such an adhesive for printed circuit board, the inventors have aimedat a sheet-shaped adhesive having a semi-cured (B-stage state) adhesivefilm and ensuring qualities such as film thickness uniformity, strengthand the like, or a prepreg adhesive formed by impregnating a semi-cured(B-stage state) adhesive into fibrous substrate and having qualitiessuch as film thickness uniformity, strength and the like.

Therefore, it is not required to control adhesive applying conditionssuch as viscosity, thixotropy and the like in the step of producing theprinted circuit board, so that the quality control of the film thicknessuniformity, strength and the like is easy and the improved adhesivelayer can be obtained, and as a result the invention has beenaccomplished.

According to a second aspect of the invention, there is the provision ofa sheet-shaped adhesive formed by applying to a base film an adhesivecomprising a semi-cured thermosetting or photosensitive heat-resistantresin matrix being insoluble in an acid or an oxidizing agent whensubjected to a curing treatment, and a cured fine powder of amino resinsoluble in an acid or an oxidizing agent and dispersed thereinto, or aprepreg adhesive formed by impregnating a fibrous substrate with anadhesive comprising a semi-cured thermosetting or photosensitiveheat-resistant resin matrix being insoluble in an acid or an oxidizingagent when subjected to a curing treatment, and a cured fine powder ofamino resin soluble in an acid or an oxidizing agent and dispersedthereinto.

According to a third aspect of the invention, there is the provision ofa method of producing printed circuit boards by forming electrolessplated conductor circuits through an adhesive layer formed on asubstrate, which comprises the steps of:

(1) forming onto a substrate an adhesive layer of an adhesive comprisingan uncured heat-resistant resin matrix insoluble in an acid or anoxidizing agent when being subjected to a curing treatment, and a curedfine powder of amino resin soluble in an acid or an oxidizing agent anddispersed thereinto;

(2) toughening a surface of said adhesive layer with an acid or anoxidizing agent; and

(3) subjecting the toughened adhesive layer to an electroless plating toform a conductor circuit.

According to a fourth aspect of the invention, the printed circuit boardobtained by the above method is a printed circuit board consisting of atoughened adhesive layer formed on at least one surface of a substrateand a conductor circuit formed on the toughened adhesive layer, saidadhesive layer being composed of an adhesive comprising an uncuredheat-resistant resin matrix insoluble in an acid or an oxidizing agentwhen subjected to a curing treatment, and a cured fine powder of aminoresin soluble in an acid or an oxidizing agent and dispersed thereinto.

In the invention, an amount of the amino resin fine powder dispersed is10-100 parts by weight based on 100 parts by weight as a solid contentof the heat-resistant resin matrix. As the amino resin fine powder,there is used at least one of melamine resin, urea resin and guanamineresin.

The heat-resistant resin matrix is a thermosetting heat-resistant resinor a photosensitive heat-resistant resin. The thermosettingheat-resistant resin matrix is a mixture of an uncured polyfunctionalepoxy resin or an uncured difunctional epoxy resin and an imidazoleseries curing agent. The photosensitive heat-resistant resin matrix isat least one photosensitive heat-resistant resin selected from uncuredpolyfunctional epoxy resin, uncured polyfunctional acryl groupcontaining resin and uncured polyfunctional acrylic resin, or a mixtureof the above resin and at least one photosensitive heat-resistant resinselected from difunctional epoxy resin and difunctional acrylic resin.

Preferably, the thermosetting heat-resistant resin matrix is a mixtureof 98-90 wt % of the thermosetting heat-resistant resin consisting of20-100 wt % as a solid content of the uncured polyfunctional epoxy resinand 80-0 wt % as a solid content of the uncured difunctional epoxy resinand 2-10 wt % as a solid content of the imidazole series curing agent.On the other hand, the photosensitive heat-resistant resin matrix is amixture of 20-100 wt % as a solid content of at least one resin selectedfrom the uncured polyfunctional epoxy resin, uncured polyfunctionalacryl group containing resin and uncured polyfunctional acrylic resinand 80-0 wt % as a solid content of at least one resin selected from theuncured difunctional epoxy resin and uncured difunctional acrylic resin.

In the printed circuit board and the method of producing the sameaccording to the invention, the adhesive layer is an adhesive layerformed by application, a sheet-shaped adhesive layer or a prepreg-likeadhesive layer. As the substrate, use may be made of a substrateprovided with conductor circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein:

FIG. 1 is a partly sectional view illustrating production steps for theformation of a first embodiment of the printed circuit board accordingto the invention;

FIGS. 2 to 14 are partly sectional views illustrating production stepsfor the formation of various embodiments of the printed circuit boardaccording to the invention, respectively; and

FIG. 15 is a schematic view illustrating migration reaction in theprinted circuit board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The adhesive for printed circuit board according to the invention willbe described in detail below.

A phenomenon that the value of surface resistivity lowers due to theaforementioned migration reaction is observed in the known adhesives.For this end, the inventors have examined a change of resistivity onvarious resins while conducting a long-period aging test underconditions that a temperature was 40° C., a humidity was 90% and avoltage was 24 V.

As a result, polyimide resins, epoxy resins and the like are known as aresin having excellent electrical properties. Among these resins, it hasbeen found that amino resins are most excellent as a resin being solublein acid or oxidizing agent and having no change of the resistivity valuewith the lapse of time, i.e. a resin causing no so-called migrationreaction.

According to the invention, therefore, since the cured amino resin finepowder soluble in acid or oxidizing agent is used as the heat-resistantresin fine powder, even when it is used under service conditions of hightemperature and high humidity atmosphere, sufficient adhesion strengthof the conductor is obtained without causing migration, fusing theconductor circuit and lowering the value of surface resistivity.Furthermore, the resistance to chemicals, heat resistance, electricalproperties and hardness become excellent.

The fine powder of amino resin for the formation of anchor recess bydispersing into the matrix is added to the heat-resistant resin matrixin an amount of 10-100 parts by weight per 100 parts by weight totalsolid content of the matrix. When the amount the fine powder added isless than 10 parts by weight, the anchors to be formed after the removalby dissolution are not clearly formed, while when it exceeds 100 partsby weight, the adhesive layer becomes porous and the adhesion strength(peel strength) between the adhesive layer and the electroless platedfilm lowers.

As the particle size of the amino resin fine powder, the averageparticle size is preferably not more than 10 μm, more particularly notmore than 5 μm. When the average particle size is more than 10 μm, thedensity of the anchors formed after the removal by dissolution becomessmall and ununiform and hence the adhesion strength and reliabilitylower. Furthermore, the unevenness of the surface in the adhesive layerbecomes violent and the fine pattern of conductors is hardly obtained,which is unfavorable in the mounting parts and the like.

The amino resin fine powder is desirable to be selected from the groupconsisting agglomerate particles having an average particle size of 2-10μm by agglomeration of heat-resistant resin powder having an averageparticle size of not more than 2 μm, a mixture of heat-resistant resinpowder having an average particle size of 2-10 μm and heat-resistantresin powder having an average particle size of not more than 2 μm, andquasi-particles obtained by adhering at least one of heat-resistantresin powder having an average particle size of 2-10 μm and inorganicfine powder having an average particle size of not more than 2 μm tosurface of heat-resistant resin powder having an average particle sizeof 2-10 μm.

The amino resin fine powder used in the invention is at least one finepowder of melamine resin, urea resin and guanamine resin. These resinshave advantages that (1) the heat resistance is excellent, (2) thesurface hardness is large, (3) the mechanical strength is excellent, (4)the electrical insulation, particularly resistance to arc discharge isexcellent, (5) the resistance to organic solvent is excellent, (6) thesolubility in acid or oxidizing agent is high, and the like.

Among these resins, the melamine resin is an addition condensate ofmelamine and formaldehyde, which produces white and water-insolubleresin through acidic reaction-or produces transparent and water-solubleresin through alkaline reaction.

That is, the melamine resin having the following chemical structure:##STR1## is obtained by reacting melamine with formaldehyde underneutral or alkaline condition to form methylol melamine, condensing themethylol melamine through dehydration and removal of formalin with acidor under heating, and then increasing the molecule through the formationof methylene bond and ether bond.

Further, the melamine resin as a molding material generally has a molarratio of formaldehyde to melamine within a range of about 1:2-1:3.Particularly, as the molar ratio becomes higher, the molded producthaving a higher hardness is produced. Therefore, melamine andformaldehyde are reacted within the above molar ratio range at 80°-90°C. while maintaining neutral or slight alkaline condition with ammoniaor the like, and then the resulting syrup is added with a base materialsuch as rayon, pulp cloth piece, asbestos, fiber or the like, which isdried and pulverized and added with pigment, releasing agent, curingagent and the like and finely pulverized to form a molding material.Moreover, the molding material is sufficiently cured by heating underpressure without adding the curing agent, but a curing agent such ascitric acid, phthalic acid, organic carboxylic acid ester or the like isgenerally used.

The urea resin having the following chemical formula: ##STR2## isobtained as a fluid containing 45-50% initial polymer by mixing urea andformalin at a molar ratio of about 1:2 and heating under neutral oralkaline condition to progress the reaction through monomethylol ureaand dimethylol urea.

The urea resin is rendered into a molding material by mixing the initialpolymer with a filler such as pulp, wood powder or the like, heating topromote polymerization, drying and pulverizing.

The guanamine resin having the following chemical structure: ##STR3## isan addition condensate between guanamine and formaldehyde obtained bythe same manner as in the melamine resin and urea resin. That is, theguanamine resin is obtained by condensing guanamine and formaldehyde bydehydration and removal of formalin in acid or through heating and thenincreasing molecule through methylene bond and ether bond.

According to the invention, a sheet-shaped adhesive having an adhesivelayer of B-stage (a state of removing only solvent without curingreaction) which guarantees qualities such as film thickness uniformity,strength and the like, or a prepreg-like adhesive formed by impregnatingan adhesive layer of B-stage which guarantees qualities such as filmthickness uniformity, strength and the like, into a fibrous substrate isused as an adhesive for printed circuit board. Because the productivityof the printed circuit board can be improved by using such an adhesivestate without damaging the electroless plating property.

That is, the adhesive for printed circuit board is rendered into thesheet-shaped adhesive having a film-like adhesive layer or theprepreg-like adhesive formed by impregnating the adhesive into thefibrous substrate, whereby the adhesive layer satisfying all propertiessuch as film thickness, peel strength and the like can previouslyprovided without controlling application conditions such as viscosity,thixotropy and the like.

As the heat-resistant resin matrix dispersing the above amino resin finepowder, there are used resins having excellent heat resistance,electrical insulation property, chemical stability and adhesion propertyand being hardly soluble in the oxidizing agent by curing treatment.

Such a thermosetting heat-resistant resin matrix is a mixture of uncuredpolyfunctional epoxy resin or uncured difunctional epoxy resin as athermosetting heat-resistant resin and an imidazole series curing agent.

Particularly, epoxy resins of bisphenol-A type, bisphenol-F type, cresolnovolac type and phenol novolac type, bismaleimido triazine resin,polyimido resin and phenolic resin are preferable as the thermosettingheat-resistant resin.

The thermosetting heat-resistant resin matrix is preferably a mixture ofa thermosetting heat-resistant resin consisting of 20-100 wt % of theuncured polyfunctional epoxy resin and 80-0wt % of the uncureddifunctional epoxy resin as a solid content and 2-10 wt % as a solidcontent of the imidazole series curing agent. When the solid content ofthe polyfunctional resin is less than 20 wt %, the hardness of theadhesive lowers and also the resistance to chemicals lowers.

Furthermore, as the photosensitive heat-resistant resin matrix, thereare used at least one photosensitive heat-resistant resin selected fromuncured polyfunctional epoxy resin, resin having uncured polyfunctionalacryl group and uncured polyfunctional acrylic resin, or a mixed resinof the above resin and at least one of difunctional epoxy resin anddifunctional acrylic resin.

Preferably, resins obtained by acrylation of phenol aralkyl type orphenol novolac type epoxy resin, acrylic resins and photosensitivepolyimido resin are used as the photosensitive heat-resistant resin.

The photosensitive heat-resistant resin matrix is preferably a mixtureof 20-100 wt % as a solid content of at least one photosensitiveheat-resistant resin selected from the uncured polyfunctional epoxyresin, the resin having uncured polyfunctional acryl group and theuncured polyfunctional acrylic resin and 80-0 wt % as a solid content ofat least one of the uncured difunctional epoxy resin and the uncureddifunctional acrylic resin. When the solid content of the polyfunctionalresin is less than 20 wt %, the hardness of the adhesive lowers and alsothe resistance to chemicals lowers.

Moreover, DICY, amine series curing agent, acid anhydride and imidazoleseries curing agent are favorable as a curing agent for theheat-resistant resin matrix. Particularly, in case of the epoxy resin,it is preferable to add the imidazole series curing agent to the matrixin an amount of 2-10 wt % per total solid content of the matrix. Whenthe amount of the imidazole series curing agent exceeds 10 wt %, thecuring is too promoted to cause brittleness, while when it is less than2 wt %, the curing is insufficient and the satisfactory hardness is notobtained.

In view of the enhancement of the Storing stability, it is advantageousthat the mixture obtained by dispersing the cured amino resin finepowder into the heat-resistant resin matrix of uncured polyfunctionalepoxy resin or uncured difunctional epoxy resin is separately storedfrom the imidazole series curing agent and then mixed therewithimmediately before the use.

As shown in FIG. 6a, the sheet-shaped adhesive may be formed by applyingan adhesive solution, which is obtained by dispersing the cured aminoresin fine powder into the heat-resistant resin matrix being hardlysoluble in acid or oxidizing agent when being subjected to a curingtreatment, onto a base film by means of a roll coater, a doctor bar orthe like and then drying and curing in a drying furnace at 60°-100° C.to form an adhesive layer of a semi-cured state.

In this case, the thickness of the adhesive layer on the base film isadjusted to 25-70 μm by a gap of the doctor bar. Since the sheet-shapedadhesive is wound on a roll, a protection film (cover film) is formed onthe adhesive layer to protect the adhesive layer of the semi-curedstate.

As the base film being the substrate of the sheet-shaped adhesive, usemay be preferably made of polyethylene terephthalate film, polypropylenefilm, polyethylene fluoride film (Tedolaf film) and the like. Thethickness of the film is desirable to be 25-50 μm. In order tofacilitate the release of the base film, silicon may be applied to thesurface of the base film contacting with the adhesive layer as areleasing agent. On the other hand, the other surface of the base filmmay be subjected to a mud treatment (roughness treatment).

The adhesive solution suitable for the formation of the adhesive layeron the base film is preferable to have a dynamic viscosity (JIS K7117),which is measured by means of a rotating viscometer at 60 rpm, of10-2,000 cps, preferably 100-300 cps. When the viscosity is less than 10cps, the adhesive layer having a sufficient peel strength is notobtained, while when the viscosity exceeds 2,000 cps, the adhesivesolution can not be applied to the base film.

Moreover, the concentration of solid content in the adhesive solution is45-75 wt %. When the concentration is less than 45 wt %, the solventundesirably remains, while when it exceeds 75 wt %, sufficientapplication property (leveling property, removal of bubbles or the like)is not obtained. And also, the ratio of amino resin fine powder toheat-resistant resin in the solid content is 1/100-200/100, preferably20/100-50/100 as a volume ratio. When the ratio is less than 1/100,distinct anchors are not formed, while when it exceeds 200/100, anchorsare too closed to each other and the sufficient strength is obtained.

In the production of the sheet-shaped adhesive, a mixture of a resinhaving a high molecular weight (hereinafter shown by R) and a resinhaving a low molecular weight (hereinafter shown by r) is used as theheat-resistant resin constituting the heat-resistant resin matrix.Preferably, the molecular weight M of the resin R is 2,000<M≦100,000,particularly 2,000≦M≦5,000, and the molecular weight m of the resin r is200<m≦2,000, particularly 300≦m≦1,000, and the mixing ratio by weight is0.2≦r/(r+R)≦0.8. Furthermore, in order that the melting point of theresin mixture is not lower than room temperature, it is favorable thatthe melting point of the resin R is within a range of 50°-150° C. andthe melting point of the resin r is within a range of not lower than 10°C. but lower than 50° C.

Among the following performances (1)-(5) required for the formation ofthe film, the resin r is effective to the performances (4)-(3), whilethe resin R is effective to the performances (4)-(5), so that when themolecular weights M, m and the mixing ratio capable of developing allthe above performances are outside the above ranges, the performances(1)-(5) lower.

(1) tackiness (tacking on the surface of the adhesive);

(2) flexibility (bending easiness);

(3) cutting property (fine cutting without cracking);

(4) edge fusion property (no flowing of the adhesive layer upon thestanding of the film); and

(5) durability to acid or oxidizing agent.

That is, when the resin mixture of the low and high molecular weights isused as the heat-resistant resin matrix, it is possible to raise thepeel strength of the adhesive layer to not less than 2 kg/cm. Althoughthis is not clear, it is considered that the resin mixture is denselyfilled in the matrix to increase the strength at breakage of the resin.Thus, the roughness of the toughened surface can be reduced to form afiner pattern.

In the production of the sheet-shaped adhesive, the average particlesize of the amino resin fine powder used is as small as possible forforming the adhesive layer film onto the base film having an excellentreleasability, and is preferably 0.05-50 μm. When the average particlesize exceeds 50 μm, the density of the anchor formed by dissolvingremoval is small and is apt to become ununiform, and hence the adhesionstrength and reliability lower. Furthermore, the unevenness of thesurface of the adhesive layer becomes violent and the film thicknessbecomes ununiform, and hence it is difficult to obtain a fine pattern ofconductors and the mounting of parts and the like becomes undesirable.

As shown in FIG. 12a, the prepreg-like adhesive may be formed byimmersing a fibrous substrate for impregnation into an adhesivesolution, which is obtained by dispersing the cured amino resin finepowder into the heat-resistant resin matrix being hardly soluble in acidor oxidizing agent when being subjected to a curing treatment, orapplying the adhesive solution onto the fibrous substrate forimpregnation by means of a roll coater, a doctor bar or the like andthen drying and curing in a drying furnace at 60°-100° C. to form anprepreg adhesive layer of a semi-cured state.

In this case, the thickness of the adhesive layer on the fibroussubstrate is usually adjusted to 25-70 μm. However, when the adhesivelayer is used so as to serve as an interlaminar insulation layer betweenmetal substrate and multilayer circuit board, the adhesive layer may bethickened by increasing the number of the layers.

As the fibrous substrate for impregnation in tile prepreg-like adhesive,use may be preferably made of heat-resistant fibers such as glass cloth,aramide fiber and the like. The thickness of the substrate is desirableto be 50-300 μm.

The adhesive solution suitable for the impregnation into the fibroussubstrate is preferable to have a dynamic viscosity (JIS K7117), whichis measured by means of a rotating viscometer at 60 rpm, of 30-200 cps,preferably 40-100 cps. When the viscosity is less than 30 cps, theadhesive layer having a sufficient peel strength is not obtained, whilewhen the Viscosity exceeds 200 cps, the adhesive solution can not beapplied to the base film.

Moreover, the concentration of solid content in the adhesive solution is30-70 wt %. When the concentration is less than 30 wt %, the solventundesirably remains, while when it exceeds 70 wt %, sufficientapplication property (leveling property, removal of bubbles or the like)is not obtained. And also, the ratio of amino resin fine powder toheat-resistant resin in the solid content is 1/100-200/100, preferably20/100-50/100 as a volume ratio. When the ratio is less than 1/100,distinct anchors are not formed, while when it exceeds 200/100, anchorsare too closed to each other and the sufficient strength is obtained.

The production of printed circuit board using the adhesive according tothe invention will be described in detail below.

(I) In the production of the printed circuit board using the adhesiveaccording to the invention, an adhesive layer is first formed on aninsulation substrate or a substrate laving conductor circuit by usingthe adhesive obtained by dispersing the cured amino resin fine powdersoluble in acid or oxidizing agent into the uncured heat-resistant resinmatrix being hardly soluble in acid or oxidizing agent when beingsubjected to a curing treatment.

As the formation of the adhesive layer on the substrate, there are amethod of applying the adhesive onto the substrate with a roll coater orthe like and then drying and curing it, and a method of piling thesheet-shaped adhesive or prepreg-like adhesive on the substrate and thenheating under pressure.

In the former method, the thickness of the adhesive layer is usuallyabout 2-40 μm. If the adhesive layer is used so as to serve as aninterlaminar insulation layer between metal substrate and multilayercircuit board, the adhesive layer may be thickened by increasing thenumber of the layers.

In the application of the adhesive, when the heat-resistant resin matrixis epoxy resin, it is preferable that a gap between coating roller anddoctor bar is 0.2-0.6 mm and a travelling speed is 0.1-3.0 m/min. Whenthe gap is wider than 0.6 mm, the scattering of the coating film is aptto be caused, while when it is narrower than 0.2 mm, it is difficult toobtain a proper film thickness. On the other hand, when the travellingspeed is slower than 0.1 m/min, the productivity is poor, while when itis faster than 3.0 m/min, the film thickness becomes ununiform.Moreover, when the heat-resistant resin matrix is a resin having anacryl group or an acrylic resin, the same result as mentioned above isobtained.

In the method using the sheet-shaped adhesive, the sheet-shaped adhesivehaving the adhesive layer of the semi-cured state after the peeling ofthe protection film is piled onto the insulation substrate having asurface roughness of Rmax=about 2 μm or the substrate having theconductor circuit so as to face the adhesive layer to the substrate andthen lamination cured or pressed under heating at 40°-120° C. under 40kg/cm² and thereafter the base film is removed to form an adhesive layerfor electroless plating.

In the method using the prepreg-like adhesive, the prepreg-like adhesivehaving the adhesive layer of the semi-cured state is laminated on theinsulation substrate having a surface roughness of Rmax=about 2 μm orthe substrate having the conductor circuit and then lamination cured orpressed under heating at 40°-120° C. under 40 kg/cm² to form an adhesivelayer for electroless plating.

The above amino resin fine powder soluble in acid or oxidizing agent isa cured heat-resistant resin. The reason for the use of the cured aminoresin fine powder is due to the fact that when the uncured amino resinfine powder is used and dispersed into a heat-resistant resin liquidforming the heat-resistant resin matrix or a solution of theheat-resistant resin as a matrix in a solvent, it dissolves into theresin liquid or the solution and hence it is impossible to develop thefunction as the amino resin fine powder.

The amino resin fine powder is produced, for example, by thermosettingthe amino resin and pulverizing it by means of a jet mill, arefrigeration pulverizer or the like, or by spray drying the amino resinsolution and then subjecting to a curing treatment, or by adding anaqueous solution of a curing agent to the uncured amino resin emulsionwith stirring and then seiving the resulting particles by means of airseiver or the like.

As a method of curing the heat-resistant resin constituting theheat-resistant resin fine powder, there are a method of curing byheating, a method of curing by addition of a catalyst and the like.Among these methods, the curing by heating is practical.

As a method of forming quasi-particles by adhering at least one of aminoresin fine powder and inorganic fine powder to the surface of the aminoresin particle, it is advantageous to use method wherein the surface ofthe amino resin particle is covered with the amino resin fine powder orthe inorganic fine powder and then heated to fuse them to each other oradhered through a binder.

As a method of forming agglomerate particles, the amino resin particlesare merely heated in a hot dryer or the like, or added and mixed with abinder and then dried, whereby the particles are agglomerated. Then, theagglomerated particles are pulverized by a ball mill, a ultrasonicdispersing machine or the like, and then seived through an air siever orthe like.

The thus obtained amino resin fine powder has not only a spherical shapebut also various complicated shapes. Therefore, the shape of theresulting anchor takes a complicated shape in accordance with the shapeof the fine powder, which effectively acts to enhance the adhesionstrengths of the plated film such as peeling strength, pulling strengthand the like.

The amino resin fine powder is added to and uniformly dispersed into theheat-resistant resin liquid constituting the heat-resistant resin matrixor the solution of the heat-resistant resin as a matrix in a solvent.

As the heat-resistant resin liquid to be added with the amino resin finepowder, the heat-resistant resin containing no solvent may be used as itis, but the solution of the heat-resistant resin in the solvent ispreferably used because the latter solution is easy in the adjustment ofthe viscosity for the uniform dispersion of the resin fine powder and iseasily applied to the substrate. As the solvent for dissolving theheat-resistant resin, use may be made of usually used solvents such asmethyl ethyl ketone, methyl cellosolve, ethyl cellosolve, butylcellosolve, butyl cellosolve acetate, butyl carbitol, butyl cellulose,tetraline, dimethylformamide, n-methyl pyrrolidone and the like.

Furthermore, the heat-resistant resin liquid may be compounded with anorganic filler such as fluorine resin, polyimide resin, benzoguanamineresin or the like, or a filler of an inorganic fine powder such assilica, alumina, titanium oxide, zirconia or the like. Other additivessuch as colorant (pigment), leveling agent, anti-foaming agent,ultraviolet absorber, flame retardant and the like may also be added.

In the manufacture of multilayer printed circuit board, via hole isformed in the adhesive layer for connecting conductor circuits to eachother.

As the method for the formation of the via hole, when the photosensitiveresin is used as the heat-resistant resin constituting the matrix it ispreferable to conduct development and etching after the exposure tolight at given positions, but the formation of the via hole throughlaser working may be adapted. On the other hand, when the thermosettingresin is used as the heat-resistant resin, it is preferable to work thegiven positions through laser or by means of a drill. The formation ofthe via hole through laser working may be conducted before or after thesurface roughening of the resin insulation layer.

As the substrate used in the invention, use may be made of plasticsubstrate, ceramic substrate, metal substrate and film substrate, anexample of which includes glass epoxy substrate, glass polyimidesubstrate, alumina substrate, low temperature fired ceramic substrate,aluminum nitride substrate, aluminum substrate, iron substrate,polyimide substrate and the like. By using these substrates,single-sided circuit board, both-sided through hole circuit board andmultilayer printed circuit board such as Cu/polyimide multilayer printedcircuit board can be prepared.

Moreover, the adhesive itself is formed to be a plate shape or a filmshape, whereby it is possible to make it a substrate having anadhesiveness capable of being subjected to an electroless plating.

(II) Next step is a treatment of roughening the surface of the adhesivelayer formed on the substrate. In this step, when the heat-resistantresin matrix is the thermosetting resin, the adhesive layer of theuncured or semi-cured state (B-stage) formed on the substrate isthermoset into a cured state (C-stage) and thereafter at least a part ofthe amino resin fine powder dispersed into the surface portion of theadhesive layer is dissolved and removed with acid or oxidizing agent toroughen the surface of the adhesive layer.

On the other hand, when the photosensitive resin is used as theheat-resistant resin matrix in the adhesive layer, a photomask is closedonto the adhesive layer of the uncured or semi-cured state (B-stage)formed on the substrate and photocured into a cured state (C-stage) andthereafter unnecessary portions are subjected to a developmenttreatment.

The removal of the amino resin fine powder dispersed onto the surfaceportion of the adhesive layer by dissolution may be carried out byimmersing the substrate provided with the adhesive layer in solution ofthe acid or oxidizing agent, or by spraying the solution of the acid oroxidizing agent onto the substrate. Thus, the surface of the adhesivelayer is roughened.

In order to effective the removal by dissolution of the heat-resistantresin fine powder, it is very effective to lightly roughen the surfaceof the adhesive layer through polishing with fine powder abrasion agentor a liquid horming.

As the oxidizing agent roughening the adhesive layer, use may be made ofchromic acid, chromate, permanganate, ozone and the like. As the acid,use may be made of hydrochloric acid, sulfuric acid, organic acid andthe like.

(III) Next step is a treatment in which the surface of the toughenedadhesive layer is subjected to an electroless plating to form anecessary conductor pattern. As the electroless plating, mention may bemade of electroless copper plating, electroless nickel plating,electroless tin plating, electroless gold plating, electroless silverplating and the like. Especially, at least one method selected fromelectroless copper plating, electroless nickel plating and electrolessgold plating is preferably used.

Moreover, according to the method of the invention, it is possible toconduct another different electroless plating or electric plating, or tocoat a soldering in addition to the above electroless plating.

In the method according to the invention, the above conductor circuitcan be formed by various methods on the known printed circuit boards.For example, there may be adopted a method of etching a circuit afterthe substrate is subjected to the electroless plating, a method ofdirectly forming a circuit at the time of electroless plating and thelike.

In case of producing the multilayer printed circuit board according tothe method of the invention, there is adopted an additive process inwhich holes for via hole are formed and then the electroless plating isconducted in the same manner as described above. Moreover, the use ofthe photosensitive resin is effective to particularly produce a build-upmulti layer printed circuit board.

According to the methods of the invention, there are obtained aone-sided printed circuit board in which a plated resist 3 and conductorcircuit 4 are formed on a substrate 1 through an adhesive layer 2 asshown in FIGS. 1f, 2f and 6f, a both-sided through hole printed circuitboard in which the plated resist 3 and the conductor circuit 4 areformed on both surfaces of the substrate 1 through the adhesive layer 2and through holes 5 as shown in FIG. 3f, and a build-up multilayerprinted circuit board in which conductor circuits (4, 6, 8, 10) areformed on a substrate 1' provided with a first conductor layer 4 throughan interlaminar layer (adhesive layer) 2 having via hole 7.

In any case, the adhesive layer is obtained by dispersing the curedamino resin fine powder soluble in acid or oxidizing agent into theuncured heat-resistant resin matrix being hardly soluble in acid oroxidizing agent when being to the curing treatment.

According to the invention, the adhesive having excellent resistance tochemicals, heat resistance, electric properties, hardness and adhesionproperty can stably be provided by using the amino resin fine powder.

Furthermore, when such an adhesive is used in form of a sheet or aprepreg, the printed circuit board can easily and cheaply be producedwithout damaging the electroless plating property.

In the printed circuit boards obtained by using the above adhesiveaccording to the invention, there is caused no migration reaction, sothat the connection reliability is high without forming short circuitbetween patterns.

The following examples are given in illustration of the invention andare not intended as limitations thereof.

EXAMPLE 1

(1) 1275 parts by weight of melamine resin was mixed with 1366 parts byweight of 37% formalin and 730 parts by weight of water, which wasadjusted to pH=9.0 with 10% sodium carbonate, held at 90° C. for 60minutes and then added with 109 parts by weight of methanol:

(2) The resulting resin liquid was dried by spray drying method toobtain a powdery resin.

(3) The resin powder was pulverized and mixed with a releasing agent anda curing catalyst in a ball mill to obtain a mixed resin powder.

(4) The mixed resin powder was placed in a mold heated at 150° C. andheld under a pressure of 250 kg/cm² for 60 minutes to obtain a shapedbody. Moreover, the mold was opened during the molding to escape gas.

(5) The shaped body was pulverized in a ball mill to obtainheat-resistant resin fine powders having particle sizes of 0.5 μm and5.5 μm, respectively.

(6) Separately, 60 parts by weight of phenol-novolac type epoxy resin(made by Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-A typeepoxy resin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) were dissolvedin butylcellosolve acetate to obtain a resin matrix composition. Then,100 parts by weight of this composition was mixed with 15 parts byweight of the above fine powder having a particle size of 0.5 μm and 30parts by weight of the above fine powder having a particle size of 5.5μm, which was kneaded through three rolls and further added withbutylcellosolve acetate to prepare an adhesive solution having a solidcontent of 75%. The viscosity of the solution was measured by means of adigital viscometer made by Tokyo Keiki Co., Ltd. at 20° C. for 60seconds according to JIS K7117 to be 5.2 Pa.s at 6 rpm and 2.6 Pa.s at60 rpm, and the value of SVI (thixotropy) was 2.0.

(7) A glass epoxy substrate 1 was toughened by polishing to form aroughened surface of JIS B0601 Rmax=2-3, and then the adhesive solutionof the above item (6) was applied onto the substrate by means of a rollcoater. In this case, a coating roll for resist of middle and highviscosity (made by Dainihon Screen Co., Ltd.) was used as the coatingroll, in which a gap between coating roll and doctor bar was 0.4 mm anda gap between coating roll and back-up roll was 1.4 mm and a travellingspeed was 400 mm/s. Thereafter, it was left to stand at a horizontalstate for 20 minutes and dried at 70° C. to obtain an adhesive layer 2having a thickness of about 50 μm (see FIGS. 1b, 1c).

(8) The substrate 1 provided with the adhesive layer 2 was immersed inan oxidizing agent consisting of an aqueous solution of 500 g/l chromicacid (CrO₃) at 70° C. for 15 minutes to roughen the surface of theadhesive layer 2, further immersed in a neutral solution (made byShipley) and washed with water. A paradium catalyst (made by Shipley)was applied to the toughened adhesive layer 2 on the substrate 1 toactivate the surface of the adhesive layer 2 (see FIG. 1d).

(9) Then, the substrate 1 was heat-treated at 120° C. in an atmosphereof nitrogen gas (10 ppm oxygen) for 30 minutes for the fixation of thecatalyst. Thereafter, a photosensitive dry film was laminated thereon,exposed to a light and developed with a modified chlorocene to form aplating resist 3 (thickness 40 μm)(see FIG. 1e).

(10) The substrate 1 having the plating resist 3 was immersed in anelectroless copper plating solution having a composition as shown in thefollowing Table 1 for 11 hours to form electroless copper plated films 4having a thickness of 25 μm (see FIG. 1f).

                  TABLE 1                                                         ______________________________________                                        copper sulfate        0.06 mol/l                                              formalin (37%)        0.30 mol/l                                              sodium hydroxide      0.35 mol/l                                              EDTA                  0.35 mol/l                                              additive              few                                                     plating temperature   70-72° C.                                        pH                    12.4                                                    ______________________________________                                    

EXAMPLE 2

(1) A suspension obtained by dispersing 200 g of melamine resinparticles (average particle size 3.9 μm) prepared in the same manner asin the items (1)-(5) of Example 1 into 5 l of acetone was added dropwisewith a suspension obtained by dispersing 300 g of melamine resin finepowder (average particle size 0.5 μm) prepared in the same manner as inthe items (1)-(5) of Example 1 into 10 l acetone with stirring in aHenshel mixer (made by Mitsui Miike Kakoki Co., Ltd.), whereby themelamine resin fine powder was adhered to the surfaces of the melamineresin particles. After the removal of acetone, they were heated at 150°C. to prepare false particles. The false particles had an averageparticle size of about 4.3 μm. Moreover, about 75% by weight of thefalse particles were existent around the above average particle sizewith a range of ±2 μm.

(2) A mixture of 50 parts by weight of the false particles prepared inthe above item (1), 60 parts by weight of phenol-novolac type epoxyresin (made by Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-Atype epoxy resin (made by Yuka Shell Co., Ltd.) and 5 parts by weight ofan imidazole curing agent (made by Shikoku Kasei Co., Ltd.) was addedwith butyl carbitol and adjusted in a homodisper dispersing machine toprepare an adhesive solution having a solid content of 80%. Theviscosity of this solution was 5.8 Pa.s at 6 rpm and 2.0 Pa.s at 60 rpm,and the value of SVI (thixotropy) was 2.9.

(3) A printed circuit board was manufactured by using the adhesivesolution in the same manner as in Example 1 (see FIG. 2).

EXAMPLE 3

(1) The melamine fine powder (average particle size 3.9 μm) obtained inthe same manner as in the items (1)-(5) of Example 1 was placed in a hotdryer and agglomerated by heating at 180° C. for 3 hours. The thusagglomerated melamine resin fine powder was dispersed into acetone,pulverized in a ball mill for 5 hours and seived in an air siever toprepare agglomerate particles. The agglomerate particles had an averageparticle size of about 3.5 μm, about 68% by weight of which was existentaround the above average particle size within a range of ±2 μm.

(2) A mixture of 50 parts by weight of the agglomerate particles preparein the above item (1), 60 parts by weight of phenol-novolac type epoxyresin (made by Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-Atype epoxy resin (made by Yuka Shell Co., Ltd.) and 4 parts by weight ofan imidazole curing agent (made by Shikoku Kasei Co., Ltd.) was addedwith butyl carbitol to prepare an adhesive solution having a solidcontent of 80%. The viscosity of this solution was 5.4 Pa.s at 6 rpm and2.0 Pa.s at 60 rpm, and the value of SVI (thixotropy) was 2.2.

(3) After both surfaces of a glass epoxy substrate 1 were roughened bypolishing to have a surface roughness of JIS B0601 Rmax=2-3 μm, theadhesive solution prepare in the above item (2) was applied to thesubstrate 1 by means of a roll coater, which was left to stand at ahorizontal state for 20 minutes and dried at 70° C. to form an adhesivelayer 2 having a thickness of about 45 82 m (see FIGS. 3b, 3c).

(4) Then, the substrate 1 provided with the adhesive layer 2 was piercedby a drill and lightly buffed to expose the filler surface and thereaterthe substrate was immersed in an aqueous solution of 6N sulfuric acid at70° C. for 15 minutes to roughen the surface of the adhesive layer 2,immersed in a neutral solution (made by Shipley) and washed with water.A paradium catalyst (made by Shipley) was applied onto the toughenedadhesive layer on the substrate 1 to activate the surface of theadhesive layer (see FIGS. 3d, 3e).

(5) The substrate 1 treated in the above item (4) was heat-treated at120° C. in an atmosphere of nitrogen gas (10 ppm oxygen) for 30 minutesfor the fixation of the catalyst. Thereafter, a photosensitive dry filmwas laminated, exposed to a light and developed with a modifiedchlorocene to form a plating resist 3 (thickness 40 μm) (see FIG. 3f).

(6) After the formation of tile plating resist 3, the substrate I wasimmersed in an electroless copper plating solution having the samecomposition as shown in Table 1 for 11 hours to form electroless copperplated films of 30 μm in thickness on both surfaces, and then conductorcircuit and through holes 5 were formed to manufacture a both-sidedprinted circuit board (see FIG. 3f).

EXAMPLE 4

(1) A photosensitive dry film (made by DuPont) was laminated onto aglass epoxy copper laminated plate (made by Toshiba Chemical ProductsCo., Ltd.) and exposed to ultraviolet ray through a mask film having adesired conductor circuit pattern. Then, it was developed with1,1,1-trichloroethane and nonconductor portion of copper was removedwith an etching solution of copper chloride and thereafter the dry filmwas peeled off with ethylene chloride. Thus, there was obtained thesubstrate having a first conductor layer 4 comprised of plural conductorpatterns (see FIG. 4a).

(2) 60 parts by weight of 50% acrylated product of cresol-novolac typeepoxy resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.), 15 parts byweight of diallyl terephthalate, 4 parts by weight of2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropanone-1 (made by CibaGeigy), 4 parts by weight of an imidazole curing agent (made by ShikokuKasei Co., Ltd.) and 50 parts by weight of hollow melamine resin finepowder (made by Honen Co., Ltd.: particle size 2 μm) were mixed andadded with butyl cellosolve, which was stirred in a homodisper agitator.Then, the mixture was kneaded through three rolls to prepare aphotosensitive adhesive layer having a solid content of 70%. Thissolution had viscosities of 5.0 Pa.s at 6 rpm and 2.5 Pa.s at 60 rpm anda SVI value of 2.0.

(3) The adhesive solution of the photosensitive resin compositionprepared in the above item (2) was applied onto the substrate 1 of theabove item (2) by means of a roll coater, which was left to stand at ahorizontal state for 20 minutes and dried at 70° C. to form aphotosensitive adhesive layer 2 having a thickness of about 50 μm (seeFIGS. 4b, 4c).

(4) A photomask film printed with black circles of 100 μm in diameterwas closed onto the substrate 1 treated in the item (3) and exposed to asuper-high vapor pressure mercury lamp at 500 mj/cm². Then, it wasdeveloped with 1,1,1-trichloroethane through ultrasonic treatment toform opening s as via holes of 100 μm in diameter on the substrate 1,which was then exposed to a super-high vapor pressure mercury lamp atabout 3000 mj/cm² and heat-treated at 100° C. for 1 hour and at 150° C.for 10 hours to form an adhesive layer 2 provided with openings 7corresponding to the photomask film and having excellent size accuracy(see FIG. 4d).

(5) The substrate 1 treated in the item (4) was immersed in an aqueoussolution of 500 g/l chromic acid (CrO₃) as an oxidizing agent at 70° C.for 15 minutes to roughen the surface of the adhesive layer 2, which wasimmersed in a neutral solution (made by Shipley) and washed with water.A paradium catalyst (made by Shipley) was applied onto the roughenedadhesive layer 2 on the substrate 1 to activate the surface of theadhesive layer 2, which was immersed in an electroless plating solutionhaving the same composition as shown in Table 1 for 11 hours to form anelectroless plated copper film 6 having a thickness of 25 μm (see FIGS.4d, 4e).

(6) By repeating the steps of the above items (3)-(5) two times wasmanufactured a build-up multilayer printed circuit board having fourcircuit layers (4,6,8,10) (see FIG. 4f).

EXAMPLE 5

(1) 60 parts by weight of phenol-novolac type epoxy resin (made by YukaShell Co., Ltd.), 40 parts by weight of bisphenol-A type epoxy resin(made by Yuka Shell Co., Ltd.) and 5 parts by weight of an imidazolecuring agent (made by Shikoku Kasei Co., Ltd.) were dissolved inbutylcellosolve acetate to obtain a resin matrix composition. Then, 100parts by weight of this composition was mixed with 15 parts by weight ofthe resin particles having a particle size of 0.5 μm and 30 parts byweight of the resin particles having a particle size of 5.5 μm asprepared in the items (1)-(5) of Example 1, which was kneaded throughthree rolls and added with butylcellosolve acetate to prepare anadhesive solution having a solid content of 75%. This solution hadviscosities of 5.2 Pa.s at 6 rpm and 2.6 Pa.s at 60 rpm as measured bymeans of a digital viscometer made by Tokyo Keiki Co., Ltd. at 20° C.for 60 seconds according to JIS K7117 and an SVI. value (thixotropy) of2.0.

(2) After the resin surface and conductor circuit surface of thesubstrate 1 having the first circuit layer 4 produced in the same manneras in the item (1) of Example 4 were toughened by polishing to have asurface roughness of JIS B0601 Rmax=2-3 μm, the adhesive solutionprepared in the above item (1) was applied to the substrate 1 by meansof a roll coater. In this application, a coating roll for resist inhigh-middle viscosity (made by Dainihon Screen Co., Ltd.) was used asthe coating roll, in which a gap between coating roll and doctor bar was0.4 mm, and a gap between coating roll and back-up roll was 1.4 mm and atravelling speed was 400 mm/s. Thereafter, it was left to stand at ahorizontal state for 20 minutes and dried at 70° C. to form an adhesivelayer 2 having a thickness of about 50 μm (see FIGS. 5b, 5c).

(3) The substrate 1 provided with the adhesive layer 2 was immersed inan aqueous solution of 500 g/l Chromic acid (CrO₃) as an oxidizing agentto roughen the surface of the adhesive layer 2, which was immersed in aneutral solution (made by Shipley) and washed with water. Further,openings 7 for via hole were formed through laser (see FIG. 5d), and aparadium catalyst (made by Shipley) was applied to the roughenedadhesive layer on the substrate 1 to activate the surface of theadhesive layer 2.

(4) The substrate 1 was heat-treated at 120° C. in an atmosphere ofnitrogen gas (10 ppm oxygen) for 30 minutes for the fixation of thecatalyst, and thereafter a photosensitive dry film was laminated andexposed to a light and developed with a modified chlorocene to form aplating resist (thickness 40 μm) (see FIG. 5e).

(5) After the formation of the plating resist 3, the substrate 1 wasimmersed in an electroless copper plating solution having the samecomposition as shown in Table 1 to form an electroless plated copperfilm 6 having a thickness of 25 μm (see FIG. 5f).

(6) By repeating the above items (2)-(5) two times was manufactured amultilayer printed circuit board (see FIG. 5g).

EXAMPLE 6

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by mixing 60 parts by weight of 60%acrylated product of cresol-novolac type epoxy resin (made by Yuka ShellCo., Ltd.), 40 parts by weight of bisphenol-A type epoxy resin (made byYuka Shell Co., Ltd.), 15 parts by weight of diallyl terephthalate, 4parts by weight of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1 (made by Ciba Geigey), 4 parts by weightof an imidazole curing agent (made by Shikoku Kasei Co., Ltd.) and 50parts by weight of hollow melamine resin particles (made by Honen Co.,Ltd.: particle size 2 μm), stirring them in a homodisper agitator whileadding butylcellosolve and kneading through three rolls to have a solidcontent of 70%. The solution had viscosities of 5.0 Pa.s at 6 rpm and2.5 Pa.s at 60 rpm and an SVI value of 2.0.

EXAMPLE 7

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by mixing 100 parts by weight of 50%acrylated product of orthocresol-novolac type epoxy resin (made by NihonKayaku Co., Ltd.), 15 parts by weight of diallyl terephthalate, 4 partsby weight of 2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropanone-1(made by Ciba Geigey), 4 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.), a photoinitiator (made by CibaGeigey) and 50 parts by weight of hollow reelamine resin particles (madeby Honen Co., Ltd.: particle size 2 μm), stirring them in a homodisperagitator while adding butylcellosolve and kneading through three rollsto have a solid content of 70%. The solution had viscosities of 5.1 Pa.sat 6 rpm and 2.6 Pa.s at 60 rpm and an SVI value of 2.0.

EXAMPLE 8

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by mixing 50 parts by weight of falseparticles prepared in the same manner as in the item (1) of Example 2,100 parts by weight of 60% acrylated product of orthocresol-novolac typeepoxy resin (made by Nihon Kayaku Co., Ltd.), 15 parts by weight ofdiallyl terephthalate, 4 parts by weight of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1 (made by CibaGeigey), 4 parts by weight of an imidazole curing agent (made by ShikokuKasei Co., Ltd.) and a photoinitiator (made by Ciba Geigey), stirringthem in a homodisper agitator while adding butylcellosolve and kneadingthrough three rolls to have a solid content of 70%. The solution hadviscosities of 5.1 Pa.s at 6 rpm and 2.6 Pa.s at 60 rpm and an SVI valueof 2.0.

EXAMPLE 9

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by dissolving 60 parts by weight ofphenol-novolac type epoxy resin (made by Yuka Shell Co., Ltd.), 40 partsby weight of difunctional acrylic resin (made by Yuka Shell Co., Ltd.)and 4 parts by weight of an imidazole curing agent (made by ShikokuKasei Co., Ltd.) in butylcellosolve acetate, mixing 100 parts by weightas a solid content of the resulting composition with 15 parts by weightof the melamine resin particles having a particle size of 0.5 μm and 30parts by weight of the melamine resin particles having a particle sizeof 5.5 μm through three rolls and adding butylcellosolve so as to have asolid content of 75%.

EXAMPLE 10

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by dissolving 60 parts by weight of 60%acrylated product of phenol-novolac type epoxy resin (made by Yuka ShellCo., Ltd.), 40 parts by weight of difunctional acrylic resin (made byYuka Shell Co., Ltd.) and 5 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.) in butylcellosolve acetate, mixing 100parts by weight as a solid content of the resulting composition with 15parts by weight of the melamine resin particles having a particle sizeof 0.5 μm and 30 parts by weight of the melamine resin particles havinga particle size of 5.5 μm through three rolls and adding butylcellosolveso as to have a solid content of 75%.

EXAMPLE 11

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by dissolving 60 parts by weight ofacrylic resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.) and 5 partsby weight of an imidazole curing agent (made by Shikoku Kasei Co., Ltd.)in butylcellosolve acetate, mixing 100 parts by weight as a solidcontent of the resulting composition with 15 parts by weight of themelamine resin particles having a particle size of 0.5 μm and 30 partsby weight of the melamine resin particles having a particle size of 5.5μm through three rolls and adding butylcellosolve so as to have a solidcontent of 75%.

EXAMPLE 12

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by dissolving 60 parts by weight ofacrylic resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofdifunctional acrylic resin (made by Yuka Shell Co., Ltd.) and 5 parts byweight of an imidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve acetate, mixing 100 parts by weight as a solid contentof time resulting composition with 15 parts by weight of the melamineresin particles having a particle size of 0.5 μm and 30 parts by weightof time melamine resin particles having a particle size of 5.5 μmthrough three rolls and adding butylcellosolve so as to have a solidcontent of 75%.

EXAMPLE 13

This example was fundamentally the same as in Example 4 except that theadhesive solution was obtained by dissolving 100 parts by weight ofacrylic resin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve acetate, mixing 100 parts by weight as a solid contentof the resulting composition with 15 parts by weight of the melamineresin particles having a particle size of 0.5 μm and 30 parts by weightof the melamine resin particles having a particle size of 5.5 μm throughthree rolls and adding butylcellosolve so as to have a solid content of75%.

EXAMPLE 14

(1) Urea and formalin were mixed at a mol ratio of 1:2 and heat-treatedat 80° C. to obtain a polymer containing 45-50 wt % of monomethylol ureaand dimethyol urea.

(2) The polymer was added with sodium phosphate and heat-treated toobtain a three-dimensional resin.

(3) The three-dimensional resin was pulverized by means of a ultrasonicjet grinder and seived with an air siever to obtain urea resin finepowder having an average particle size of 0.8 μm.

(4) This example was fundamentally the same as in Example 1 except thatthe urea resin fine powder obtained in the above items (1)-(3) was usedas the amino resin fine powder. Moreover, the adhesive solution hadviscosities of 5.0 Pa.s at 6 rpm and 2.5 Pa.s at 60 rpm as measured bymeans of a digital viscometer made by Tokyo Keiki Co., Ltd. at 20° C.for 60 seconds and an SVI value (thixotropy) of 2.0.

EXAMPLE 15

(1) A mixture of 500 parts by weight of melamine resin, 750 parts byweight of acetoguanamine resin, 1200 parts by weight of 37% formalin and800 parts by weight of water was used as a starting material and curedand pulverized in the same manner as in the items (1)-(5) of Example 1to obtain fine powder of melamine-acetoguanamine cocondensed resin.

EXAMPLE 16

(1) A resin matrix composition was obtained by dissolving 60 parts byweight of phenol-novolac type epoxy resin (made by Nihon Kayaku Co.,Ltd.: molecular weight=3600, mp=90° C.), 40 parts by weight ofbisphenol-A type epoxy resin (made by. Yuka Shell Co., Ltd.: molecularweight=900, mp=64° C.) and 5 parts by weight of an imidazole curingagent (made by Shikoku Shell Co., Ltd.) in butylcellosolve acetate.Then, 100 parts by weight as a solid content of the composition wasmixed with 15 parts by weight of the melamine resin fine powder having aparticle size of 0.5 μm and 30 parts by weight of the melamine resinfine powder having a particle size of 5.5 μm obtained in the same manneras in the items (1)-(5) of Example 1 in a ball mill and added withbutylcellosolve acetate to prepare an adhesive solution having a solidcontent of 60%. This solution had a viscosity of 0.2 Pa.s at 60 rpm asmeasured by means of a digital viscometer at 20° C. for 60 secondsaccording to JIS K7117.

(2) The adhesive solution was applied to a PET (polyethyleneterephthalate) film 14 coated at its surface with silicon coat through adoctor blade 16 and dried in an IR furnace 15 at 80° C. for 20 minutesto provide B-stage (semi-cured state) and further a cover film 11 ofpolyethylene (for protecting the surface of the adhesive) was laminatedthereon to prepare a sheet-shaped adhesive (see FIG. 6a).

(3) After a glass epoxy substrate 1 was roughened at both surfaces bypolishing to have a surface roughness of JIS B0601 Rmax=2-3 μm, thesheet-shaped adhesive of the item (2) was laminated onto the toughenedsurface of the substrate and heated at 80° C. under a pressure of 3kg/cm² to form an adhesive layer 2 having a thickness of about 50 μm(see FIGS. 6b, 6c).

(4) The both-sided printed circuit board was manufactured by the samemethod as in the items (8)-(10) of Example 1 (see FIG. 6).

EXAMPLE 17

(1) An adhesive solution having a solid content of 55% was prepared bydissolving 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 40 parts by weight bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve, mixing 100 parts by weight as a solid content of theresulting composition with 15 parts by weight of melamine resin finepowder (made by Honen Co., Ltd.) having a particle size of 0.5 μm and 30parts by weight of the melamine resin fine powder having a particle sizeof 5.5 μm pulverized in a ball mill, kneading through three rolls andadding butylcellosolve thereto. This solution had viscosities of 2.6Pa.s at 6 rpm and 1.0 Pa.s at 60 rpm and an SVI value (thixotropy) of2.6.

(2) The adhesive was applied to a polyethylene film 11 provided with asilicon coating by means of a roll coater and dried by heating at 120°C. for 30 minutes to obtain a sheet-shaped adhesive (see FIGS. 7a, 7b).

(3) The sheet-shaped adhesive was piled onto the substrate 1, and afterthe polyethylene film 11 was peeled off, it was pressed under heating toobtain an adhesive layer 2 (see FIGS. 7c, 7d).

(4) A printed circuit board was manufactured in the same manner as inthe items (8)-(10) of Example 1 (see FIG. 7).

EXAMPLE 18

(1) An adhesive solution having a solid content of 50% was prepared byadding butyl carbitol to a mixture of 50 parts by weight of falseparticles prepared in the same manner as in the item (1) of Example 2,30 parts by weight of cresol-novolac type epoxy resin (made by NihonKayaku Co., Ltd.: molecular weight=2500, mp=60° C.), 40 parts by weightof phenol-novolac type epoxy resin (made by Yuka Shell Co., Ltd.:molecular weight=700, mp=40° C.), 30 parts by weight of bisphenol-A typeepoxy resin (made by Yuka Shell Co., Ltd.: molecular weight=500, mp=25°C.) and 5 parts by weight of an imidazole-curing agent (made by ShikokuKasei Co., Ltd.) and adjusting in a homodisper dispersing machine. Theviscosity of this solution was 0.1 Pa.s at 60 rpm.

(2) The adhesive solution was applied to a Tedolaf film 12 (made byDuPont) by means of a doctor blade, dried in a continuous furnace 15 at100° C. for 5 minutes to provide B-stage (semi-cured state) and a coverfilm 11 of polyethylene (for protecting the adhesive surface) waslaminated thereon to form a sheet-shaped adhesive (see FIG. 8a).

(3) A both-sided printed circuit board was manufactured in the samemanner as in Example 16 (see FIG. 8).

EXAMPLE 19

(7) An adhesive solution having a solid content of 65% was prepared bydissolving 50 parts by weight of false particles prepared in the samemanner as in the item (1) of Example 3, 80 parts by weight of specialfunctional epoxy resin (made by Nihon Kayaku Co., Ltd.: molecularweight=3200, mp=60° C.), 20 parts by weight of bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.: molecular weight=500, mp=25° C.)and 7 parts by weight of a quazole curing agent (made by Shikoku KaseiCo., Ltd.) in butyl carbitol. The viscosity of this solution was 0.3Pa.s at 60 rpm.

(2) The adhesive solution was applied to a commercially availableprepreg 13 by means of a doctor blade 16 and dried at 100° C. for 5minutes to provide B-stage (semi-cured state) and a cover film 11 ofpolyethylene (for protecting the adhesive surface) and further PET(polyethylene terephthalate) film 14 for protecting the adhesive layer 2were laminated thereon to prepare a sheet-shaped adhesive (see FIG. 9a).

(3) While peeling off the cover film 11, 5 commercially availableprepregs and the sheet-shaped adhesive were piled one upon the other soas to contact with the adhesive layer 2, which was pressed at 150° C.and 50 kg/cm² for 200 minutes and thereafter the PET film 14 was peeledoff to obtain the substrate 1 provided at both surfaces with theadhesive layers 2 (see FIGS. 9b, 9c).

(4) A printed circuit board was manufactured in the same manner as inthe items (4)-(6) of Example 3. (see FIG. 9).

EXAMPLE 20

This example was fundamentally the same as in Example 15 except that theadhesive solution was obtained by dissolving 50 parts by weight ofspecial trifunctional epoxy resin (molecular weight=3000, mp=80° C.), 50parts by weight of novolac type polyfunctional epoxy resin (molecularweight=500, mp=35° C.) and 7 parts by weight of an imidazole curingagent (made by Shikoku Kasei Co., Ltd.) in butylcellosolve acetate,mixing 100 parts by weight as a solid content of the resultingcomposition with 15 parts by weight of melamine resin fine powder havinga particle size of 0.5 μm and 30 parts by weight of the melamine resinfine powder having a particle size of 5.5 μm obtained by the same methodas in the items (1)-(5) of Example 1 in a ball mill and further addingbutylcellosolve to provide a solid content of 455. This solution had aviscosity of 0.1 Pa.s at 60 rpm as measured by means of a digitalviscometer at 20° C. for 60 seconds according to JIS K7117.

EXAMPLE 21

(1) 80 parts by weight of 50% acrylated product of cresol-novolac typeepoxy resin (made by Yuka Shell Co., Ltd.), 20 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.), 15 parts byweight of diallyl terephthalate, 4 parts by weight of2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropanone-1 (made by CibaGeigey), 4 parts by weight of an imidazole curing agent and 50 parts byweight of hollow melamine resin fine powder (made by Honen Co., Ltd.:particle size 2 μm) were mixed and added with a leveling agent, whichwas stirred in a homodisper agitator while adding butylcellosolve andthen kneaded in a ball mill to prepare a photosensitive adhesivesolution having a solid content of 50%. The viscosity of this solutionwas 0.5 Pa.s at 60 rpm.

(2) The adhesive solution was applied to a polypropylene film 12provided with a silicon coat in the same manner as in Example 14 toprepare a sheet-shaped photosensitive adhesive.

(3). Then, the sheet-shaped photosensitive adhesive of the item (2) waspiled on the substrate 1 provided with first circuit layer 4 prepare inthe same manner as in the item (1) of Example 4 and heated at 80° C.under a pressure of 3 kg/cm² to form an adhesive layer 2 (see FIGS. 10b,10c).

(4) A photomask film printed by black circles of 100 μm in diameter wasclosed to the substrate 1 treated in the above item (3) and exposed to asuper-high vapor pressure mercury lamp at 500 mj/cm². This was subjectedto ultrasonic developing treatment with 1,1,1-trichloroethane to formopening for via hole of 100 μm in diameter on the circuit board 1',which was further exposed to a super-high vapor pressure mercury lamp atabout 3000 mj/cm² and heated at 100° C. for 1 hour and further at 150°C. for 10 hours to form an adhesive layer 2 provided with openings 7corresponding to the photomask film and having excellent size accuracy(see FIG. 10d).

(5) The substrate 1 treated in the item (4) was immersed in an aqueoussolution of 500 g/l chromic acid (CrO₃) as an oxidizing agent at 70° C.for 15 minutes to roughen the surface of the adhesive layer 2, which wasimmersed in a neutral solution (made by Shipley) and washed with water.A paradium catalyst (made by Shipley) was applied to the toughenedadhesive layer 2 on the substrate 1 to activate the surface of theadhesive layer 2 (see FIG. 10d).

(6) The substrate 1 was heat-treated at 120° C. in an atmosphere ofnitrogen gas (10 ppm oxygen) for 30 minutes for the fixation of thecatalyst. Thereafter, a photosensitive dry film was laminated, exposedto a light and developed with a modified chlorocene to form a platingresist 3 (thickness 40 μm) (see FIG. 10e).

(7) Further, the substrate 1 provided with the plating resist 3 wasimmersed in an electroless copper plating solution having the samecomposition as shown in Table 1 for 11 hours to form an electrolesscopper plated film having a thickness of 25 μm (see FIG. 10f).

(8) The plating resist 3 was dissolved and removed with methylenechloride (see FIG. 10f).

(9) By repeating the steps of the items (3)-(8) was manufactured abuild-up multilayer printed circuit board having four circuit layers (4,6, 8, 10) (see FIG. 10g).

EXAMPLE 22

(1) An adhesive solution having a solid content of 55% was prepared bydissolving 60 parts by weight of 60% acrylated product of phenol-novolactype epoxy resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.), 4 parts byweight of an imidazole curing agent (made by Shikoku Kasei Co., Ltd.),15 parts by weight of diallyl terephthalate and 4 parts by weight of2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropanone-1 (made by CibaGeigey) in butylcellosolve, mixing 100 parts by weight as a solidcontent of the resulting composition with 15 parts by weight of melamineresin fine powder (made by Honen Co., Ltd.) having a particle size of0.5 μm and 30 parts by weight of the melamine resin fine powder having aparticle size of 5.5 μm pulverized in a ball mill, kneading throughthree rolls and adding butycellosolve. This solution had viscosities of2.6 Pa.s at 6 rpm and 1.0 Pa.s at 60 rpm and an SVI value (thixotropy)of 2.6.

(2) The adhesive solution was applied to a polyethylene film 12 providedwith a silicon coating by means of a roll coater and dried by heating at120° C. for 30 minutes to form a sheet-shaped adhesive (see FIGS. 11a,11b).

(3) The sheet-shaped adhesive of the item (2) was piled on the substrate1 provided with the first circuit layer 4 in the same manner as inExample 4, and after the polyethylene film 12 was peeled off, it waspressed by heating to form an adhesive layer 2 (see FIGS. 11c, 11d,11e).

(4) A multilayer printed circuit board was manufactured by the samemethod as in the items (4)-(6) of Example 4 (see FIG. 11).

EXAMPLE 23

(1) An adhesive solution having a solid content of 50% was prepared bydissolving 50 parts by weight of 75% acrylated product of cresol-novolactype epoxy resin (made by Yuka Shell Co., Ltd.), 50 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.) and 4 partsby weight of an imidazole curing agent (made by Shikofu Kasei Co., Ltd.)in butylcellosolve acetate, mixing 100 parts by weight as a solidcontent of the resulting composition with 15 parts by weight of melamineresin fine powder (made by Honen Co., Ltd.) having a particle size of0.5 μm and 30 parts by weight of the melamine resin fine powder having aparticle size of 5.5 μm pulverized in a ball mill and further addingbutylcellosolve acetate. The viscosity of the solution was 0.3 Pa.s at60 rpm as measured by means of a digital viscometer at 20° C. for 60seconds according to JIS K7117.

(2) Then, the adhesive solution was applied to a Tedolaf film 12provided with silicon coating and dried by heating at 80° C. for 30minutes to prepare a photosensitive sheet-shaped adhesive.

(3) A build-up multilayer printed circuit board was manufactured byusing the sheet-shaped adhesive in the same manner as in Example 21 (seeFIG. 10).

EXAMPLE 24

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 45% was obtained bydissolving 60 parts by weight of 50% acrylated product of cresol-novolactype epoxy resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofbisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.), 4 parts byweight of 2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropanone-1(made by Ciba Geigey) and 4 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.) in butylcellosolve acetate, mixing 100parts by weight as a solid content of the resulting composition with 15parts by weight of melamine resin fine powder (made by Honen Co., Ltd.)having a particle size of 0.5 μm and 30 parts by weight of the melamineresin powder having a particle size of 5.5 μm pulverized in a ball milland further adding butylcellosolve acetate. The viscosity of thesolution was 0.1 Pa.s at 60 rpm as measured by means of a digitalviscometer at 20° C for 60 seconds according to JIS K7117.

EXAMPLE 25

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 50% was obtained bydissolving 60 parts by weight of 50% acrylated product oforthocresol-novolac type epoxy resin (made by Nihon Kayaku Co., Ltd.),40 parts by weight of bisphenol-F type epoxy resin (made by Yuka ShellCo., Ltd.), 15 parts by weight of diallyl terephthalate, 4 parts byweight of 2-methyl-1-[4-(methylthto)phenyl]-2-morpholinopropanone-1(made by Ciba Geigey), 4 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.), a photoinitiator (made by CibaGeigey) and 50 parts by weight of hollow melamine resin fine powder(made by Honen Co., Ltd.: particle size 2 μm) in butylcellosolveacetate, stirring in a homodisper agitator and kneading in a ball mill.The viscosity of the solution was 0.2 Pa.s at 60 rpm as measured bymeans of a digital viscometer at 20° C. for 60 seconds according to JISK7117.

EXAMPLE 26

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 60% was obtained bydissolving 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 40 parts by weight of difunctional acrylicresin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve acetate, mixing 100 parts by weight as a solid contentof the resulting composition with 15 parts by weight of melamine resinfine powder having a particle size of 0.5 μm and 30 parts by weight ofthe melamine resin fine powder having a particle size of 5.5 μm,kneading through three rolls and further adding butylcellosolve acetate.

EXAMPLE 27

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 65% was obtained bydissolving 60 parts by weight of 60% acrylated product of phenol-novolactype epoxy resin (made by Yuka Shell Co., Ltd.), 40 parts by weight ofdifunctional acrylic resin (made by Yuka Shell Co., Ltd.) and 5 parts byweight of an imidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve acetate, mixing 100 parts by weight as a solid contentof the resulting composition with 15 parts by weight of melamine resinfine powder having a particle size of 0.5 μm and 30 parts by weight ofthe melamine resin fine powder having a particle size of 5.5 μm,kneading through three rolls and further adding butylcellosolve acetate.

EXAMPLE 28

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 65% was obtained bydissolving 60 parts by weight of acrylic resin (made by Yuka Shell Co.,Ltd.), 40 parts by weight of bisphenol-A type epoxy resin (made by YukaShell Co., Ltd.) and 5 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.) in butylcellosolve acetate, mixing 100parts by weight as a solid content of the resulting composition with 15parts by weight of melamine resin fine powder having a particle size of0.5 μm and 30 parts by weight of the melamine resin fine powder having aparticle size of 5.5 μm, kneading through three rolls and further addingbutylcellosolve acetate.

EXAMPLE 29

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 55% was obtained bydissolving 60 parts by weight of acrylic resin (made by Yuka Shell Co.,Ltd.), 40 parts by weight of difunctional acrylic resin (made by YukaShell Co., Ltd.) and 5 parts by weight of an imidazole curing agent(made by Shikoku Kasei Co., Ltd.) in butylcellosolve acetate, mixing 100parts by weight as a solid content of the resulting composition with 15parts by weight of melamine resin fine powder having a particle size of0.5 μm and 30 parts by weight of the melamine resin fine powder laving aparticle size of 5.5 μm, kneading through three rolls and further addingbutylcellosolve acetate.

EXAMPLE 30

This example was fundamentally the same as in Example 21 except that theadhesive solution having a solid content of 55% was obtained bydissolving 100 parts by weight of acrylic resin (made by Shin NakamuraKagaku Co., Ltd.) and 5 parts by weight of an imidazole curing agent(made by Shikoku Kaset Co., Ltd.) in butylcellosolve acetate, mixing 100parts by weight as a solid content of the resulting composition with 15parts by weight of melamine resin fine powder having a particle size of0.5 μm and 30 parts by weight of the melamine resin fine powder having aparticle size of 5.5 μm, kneading through three rolls and further addingbutylcellosolve acetate.

EXAMPLE 31

(1) Formalin was mixed with guanamine at a molar ratio of 1.2-1.6 to 1,adjusted to p=6.5 and reacted at 60° C. to obtain a transparent resinliquid.

(2) The resin liquid was dried, roughly pulverized, placed in a ballmill together with phosphoric acid and plasticizer, cured and finelypulverized to obtain fine powder of guanamine resin.

(3) This example was fundamentally the same as in Example 16 except thatthe guanamine resin fine powder obtained in the above items (1), (2) wasused as the amino resin fine powder. Moreover, the viscosity of theadhesive solution was 5.0 Pa.s at 6 rpm as measured by means of adigital viscometer at 20° C. for 60 seconds according to JIS K7117.

EXAMPLE 32

(1) An adhesive solution having a solid content of 60% was prepared bydissolving 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) inbutylcellosolve acetate to form a resin matrix composition, mixing 100parts by weight as a solid content of tile composition with 15 parts byweight of melamine resin fine powder having a particle size of 0.5 μmand 30 parts by weight of the melamine resin fine powder having aparticle size of 5.5 μm, which were obtained by the same method as inthe items (1)-(5) of Example 1, in a ball mill, kneading in a pearl milland further adding methyl ethyl ketone. The viscosity of the solutionwas 0.05 Pa.s at 60 rpm as measured by means of a digital viscometer at20° C. for 60 seconds according to JIS K7117.

(2) The adhesive solution was passed through an apparatus consisting ofimmersion, squeezing, drying and cutting to prepare a prepreg-likeadhesive. That is, a galls cloth 18 was immersed in the adhesivesolution 17 placed in a tank capable of being stirred under ultrasonicstate, squeezed out between squeeze rolls, dried in an IR furnace 15 at100° C. for 10 minutes and cut to prepare a prepreg-like adhesive (seeFIG. 12a).

(3) Glass epoxy prepregs were sandwiched between the prepreg-likeadhesives prepared in the item (2) as an outermost layer so as to have athickness of 1.6 mm, which was treated at 100° C. under a contactpressure of 1 minute and pressed at 100° C. under a pressure of 50kg/cm² for 20 minutes and then cured at 150° C. for 3 hours to form anadhesive layer 2 onto a substrate 1 (see FIG. 12b).

(4) A printed circuit board was manufactured in the same manner as inthe items (8)-(10) of Example 1 (see FIG. 12).

EXAMPLE 33

(1) An adhesive solution was prepared by adding methyl ethyl ketone to amixture of 50 parts by weight of false particles prepared in the samemanner as in the item (1) of Example 2, 60 parts by weight ofphenol-novolac type epoxy resin (made by Yuka Shell Co., Ltd.), 30 partsby weight of bisphenol-A type epoxy resin (made by Yuka Shell Co., Ltd.)and 5 parts by weight of an imidazole curing agent (made by ShikokuKasei Co., Ltd.) so as to have a solid content of 30% and then kneadingin a pearl mill. The viscosity of the solution was 0.06 Pa.s at 60 rpm.

(2) The adhesive solution 17 was impregnated into aramide fiber cloth 18in the same manner as in Example 32 to prepare a preprag-like adhesive.

(3) A printed circuit board was manufactured by using the preprag-likeadhesive of the item (3) in the same manner as in Example 32 (see FIG.12).

EXAMPLE 34

(1) An adhesive solution having a solid content of 65% was prepared byadding butylcellosolve acetate to a mixture of 50 parts by weight offalse particles prepared in the same manner as in the item (1) ofExample 3, 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 20 parts by weight of bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.) and 4 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.), kneadingthrough three rolls, stirring in a homodisper agitator and furtheradding butylcellosolve acetate. The viscosity of the solution was 0.04Pa.s at 60 rpm.

(2) The adhesive solution was applied onto a glass epoxy preprag bymeans of a roll coater, which was left to stand at a horizontal statefor 20 minutes and dried at 70° C. to form a prepreg-like adhesiveprovided with an adhesive layer 2 of 45 μin thickness (see FIG. 13a).

(3) An adhesive layer 2 was formed on a substrate 1 by using theprepreg-like adhesive of the item (2) in the same manner as described inExample 32 (see FIG. 13b).

(4) A both-sided printed circuit board was manufactured in the samemanner as in the items (4)-(6) of Example 3 (see FIG. 13).

EXAMPLE 35

(1) An adhesive solution having a solid content of 55% was prepared bydissolving a mixture of 60 parts by weight of phenol-novolac type epoxyresin (made by Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-Atype epoxy resin (made by Yuka Shell Co., Ltd.) and 5 parts by weight ofan imidazole curing agent (made by Shikoku Kasei Co., Ltd.) in methylethyl ketone, mixing 100 parts by weight as a solid content of theresulting composition with 15 parts by weight of melamine resin finepowder (made by Honen Co., Ltd.) having a particle size of 0.5 μm and 30parts by weight of of the melamine resin fine powder having a particlesize of 5.5 μm in a ball mill and further adding methyl ethyl ketone.The viscosity of the solution was 0.05 Pa.s at 60 rpm as measured bymeans of a digital viscometer at 20° C. for 60 seconds according to JISK7117.

(2) A prepreg-like adhesive was prepared by impregnating a glass cloth18 with the adhesive solution of the above item (1) in the same manneras in the item (2) of Example 32 (see FIG. 14a).

(3) The prepreg-like adhesive of the item (2) was piled on the substrate1 provided with a first circuit layer 4 in the same manner as if theitem (1) of Example 4 and pressed by heating to form an adhesive layer 2(see FIG. 14b).

(4) A both-sided printed circuit board was manufactured by subjectingthe substrate 1 provided with the adhesive layer 2 to the same treatmentas in the items (4)-(6) of Example 3 (see FIG. 14).

EXAMPLE 36

(1) An adhesive solution having a solid content of 80% was prepared bydissolving a mixture of 60 parts by weight of cresol-novolac type epoxyresin (made by Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-Atype epoxy resin (made by Yuka Shell Co., Ltd.) and 5 parts by weight ofan imidazole curing agent (made by Shikoku Kasei Co., Ltd.) inmethylcellosolve, mixing 100 parts by weight as a solid content of theresulting composition with 50 parts by weight of melamine resin finepowder (made by Honen Co., Ltd.: particle size 3 μm) pulverized in aball mill, kneading through three rolls and further addingmethylcellosolve. The viscosity of the solution was 0.04 Pa.s at 60 rpmas measured by means of a digital viscometer at 20° C. for 60 secondsaccording to JIS K7117.

(2) The adhesive solution was applied to a glass epoxy prepreg by meansof a doctor bar and then dried at 80° C. to obtain a prepreg-likeadhesive provided with an adhesive layer 2 having a thickness of 50 μm.

(3) A both-sided printed circuit board was manufactured by using theprepreg-like adhesive of the above item (2) in the same manner as inExample 35.

EXAMPLE 37

This example was fundamentally the same as in Example 32 except that theadhesive solution having a solid content of 40% was obtained bydissolving 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) in methyl ethylketone, mixing 100 parts by weight as a solid content of the resultingcomposition with 50 parts by weight of hollow melamine resin fine powder(made by Honen Co., Ltd.), kneading in a pearl mill and further addingmethyl ethyl ketone. Moreover, the viscosity of the solution was 0.05Pa.s at 60 rpm as measured by means of a digital viscometer at 20° C.for 60 seconds according to JIS K7117.

EXAMPLE 38

This example was fundamentally the same as in Example 32 except that theadhesive solution having a solid content of 55% was obtained bydissolving 60 parts by weight of phenol-novolac type epoxy resin (madeby Yuka Shell Co., Ltd.), 40 parts by weight of bisphenol-A type epoxyresin (made by Yuka Shell Co., Ltd.) and 5 parts by weight of animidazole curing agent (made by Shikoku Kasei Co., Ltd.) in methyl ethylketone, mixing 100 parts by weight as a solid content of the resultingcomposition with 50 parts by weight of false particles prepared in thesame manner as in the item (1) of Example 3, kneading in a ball mill andfurther adding methyl ethyl ketone. Moreover, the solution hadviscosities of 0.6 Pa.s at 6 rpm and 0.5 Pa.s at 60 rpm and an SVI value(thixotropy) of 1.2.

EXAMPLE 39

(1) Urea, isothiourea and formalin were mixed at a molar ratio of 1:1:2and cocondensed by heating at 80° C. to obtain urea-thiourea cocondensedresin fine powder.

(2) This example was fundamentally the same as in Example 32 except thatthe urea-thiourea cocondensed resin fine powder obtained in the item (1)was used as the amino resin fine powder. Moreover, the viscosity of thesolution was 0.05 Pa.s at 6 rpm as measured by means of a digitalviscometer at 20° C. for 60 seconds according to JIS K7117.

EXAMPLE 40

(1) An adhesive solution A was prepared by the same treatment as in theitems (1)-(6) of Example 1 (except that the curing agent was not used).

(2) An adhesive solution B was prepared by dissolving 5 parts by weightof an imidazole curing agent in butylcellosolve.

(3) The adhesive solutions A and B were stored at room temperature for 1month and mixed to obtain an adhesive solution, The properties of thissolution were the same as in Example 1.

(4) A printed circuit board was manufactured by using the above adhesivesolution in the same manner as in Example 1. The properties of theresulting board were the same as in Example 1.

EXAMPLE 41

A multilayer printed circuit board was manufactured by using the sameadhesive solution as in Example 40 in the same manner as in Example 5.The properties of the resulting board were the same as in Example 5.

EXAMPLE 42

A printed circuit board was manufactured by using the same adhesivesolution as in Example 40 in the same manner as in Example 32. Theproperties of the resulting board were the same as in Example 32.

EXAMPLE 43

This example was fundamentally the same as in Example 1 except that theadhesive solution having a solid content of 75% was obtained bydissolving 100 parts by weight of nonflammable novolac type epoxy resin(made by Nihon Kayaku Co., Ltd.) and 7 parts by weight of an imidazolecuring agent (made by Shikoku Kasei Co., Ltd.) in butylcellosolveacetate, mixing 100 parts by weight as a solid content of the resultingcomposition with 15 parts by weight of the resin particles obtained inthe items (1)-(6) of Example 1 having a particle size of 0.5 μm and 30parts by weight of the above resin particles having a particle size of5.5 μm, kneading through three rolls and further adding butylcellosolveacetate. Moreover, the solution had viscosities of 5.2 Pa.s at 6 rpm and2.5 Pa.s at 60 rpm and an SVI value (thixotropy) of 2.0.

EXAMPLE 44

This example was fundamentally the same as in Example 5 except that theadhesive solution having a solid content of 75% was obtained bydissolving 100 parts by weight of nonflammable novolac type epoxy resin(made by Nihon Kayaku Co., Ltd.) and 7 parts by weight of an imidazolecuring agent (made by Shikoku Kasei Co., Ltd.) in butylcellosolveacetate, mixing 100 parts by weight as a solid content of the resultingcomposition with 15 parts by weight of the resin particles obtained inthe items (1)-(6) of Example 1 having a particle size of 0.5 μm and 30parts by weight of the above resin particles having a particle size of5.5 μm, kneading through three rolls and further adding butylcellosolveacetate. Moreover, the solution lad viscosities of 5.2 Pa.s at 6 rpm and2.5 Pa.s at 60 rpm and an SVI value (thixotropy) of 2.0.

EXAMPLE 45

This example was fundamentally the same as in Example 32 except that theadhesive solution having a solid content of 75% was obtained bydissolving 100 parts by weight of nonflammable novolac type epoxy resin(made by Nihon Kayaku Co., Ltd.) and 7 parts by weight of an imidazolecuring agent (made by Shikoku Kasei Co., Ltd.) in butylcellosolveacetate, mixing 100 parts by weight as a solid content of the resultingcomposition with 15 parts by weight of the resin particles obtained inthe items (1)-(6) of Example 1 having a particle size of 0.5 μm and 30parts by weight of the above resin particles having a particle size of5.5 μm, kneading through three rolls and further adding butylcellosolveacetate. Moreover, the solution had viscosities of 5.2 Pa.s at 6 rpm and2.5 Pa.s at 60 rpm and an SVI value (thixotropy) of 2.0.

In the above examples, the epoxy resin was used as a matrix because theepoxy resin hardly soluble in the acid or oxidizing agent was large inthe crosslinking density and the ionic compound hardly moved to cause nomigration.

COMPARATIVE EXAMPLE 1

A printed circuit board was produced in the same manner as in Example 1except that an epoxy resin cured by a dicyano series curing agent wasused as a heat-resistant resin fine powder.

COMPARATIVE EXAMPLE 2

A printed circuit board was produced in the same manner as in Example 4except that an epoxy resin cured by a dicyano series curing agent wasused as a heat-resistant resin fine powder.

COMPARATIVE EXAMPLE 3

A printed circuit board was produced in the same manner as in Example 14except that an epoxy resin cured by anhydrous pyromellitic acid was usedas a heat-resistant resin fine powder.

COMPARATIVE EXAMPLE 4

A printed circuit board was produced in the same manner as in Example 27except that an epoxy resin cured by anhydrous trimellitic acid was usedas a heat-resistant resin fine powder.

The adhesion property (peeling strength), electric property (electricalinsulating quality), hardness (Barcol viscosity) and influence ofimpurity (resistance to migration) of the electroless plated film in theprinted circuit board and the solubility of the amino resin fine powderin acid or oxidizing agent were measured to obtain results as shown inTable 2.

                  TABLE 2                                                         ______________________________________                                        Peeling     Electrical                Solubility                              strength    ensulating                                                                              Hard-    Impurity                                                                             of                                      (kg/cm)     quality   ness     influence                                                                            melamine                                ______________________________________                                        Example                                                                        1     1.9      ◯                                                                           60     ◯                                                                        300                                    2     1.8      ◯                                                                           50     ◯                                                                        350                                    3     1.8      ◯                                                                           60     ◯                                                                        250                                    4     1.9      ◯                                                                           55     ◯                                                                        220                                    5     1.8      ◯                                                                           52     ◯                                                                        300                                    6     1.8      ◯                                                                           61     ◯                                                                        310                                    7     1.8      ◯                                                                           60     ◯                                                                        310                                    8     1.9      ◯                                                                           61     ◯                                                                        290                                    9     1.8      ◯                                                                           61     ◯                                                                        290                                   10     1.8      ◯                                                                           62     ◯                                                                        300                                   11     1.8      ◯                                                                           60     ◯                                                                        300                                   12     1.9      ◯                                                                           61     ◯                                                                        300                                   13     1.8      ◯                                                                           61     ◯                                                                        290                                   14     1.9      ◯                                                                           60     ◯                                                                        310                                   15     1.8      ◯                                                                           60     ◯                                                                        300                                   16     2.2      ◯                                                                           61     ◯                                                                        301                                   17     1.9      ◯                                                                           65     ◯                                                                        200                                   18     2.0      ◯                                                                           62     ◯                                                                        300                                   19     2.1      ◯                                                                           60     ◯                                                                        300                                   20     2.0      ◯                                                                           60     ◯                                                                        310                                   21     2.1      ◯                                                                           61     ◯                                                                        310                                   22     1.9      ◯                                                                           63     ◯                                                                        255                                   23     2.1      ◯                                                                           60     ◯                                                                        300                                   24     2.1      ◯                                                                           62     ◯                                                                        310                                   25     2.0      ◯                                                                           60     ◯                                                                        300                                   26     2.0      ◯                                                                           60     ◯                                                                        310                                   27     2.1      ◯                                                                           61     ◯                                                                        310                                   28     1.8      ◯                                                                           62     ◯                                                                        310                                   29     1.9      ◯                                                                           60     ◯                                                                        310                                   30     1.9      ◯                                                                           60     ◯                                                                        300                                   31     2.0      ◯    ◯                                32     1.8      ◯                                                                           61     ◯                                                                        301                                   33     1.8      ◯                                                                           55     ◯                                                                        355                                   34     1.9      ◯                                                                           58     ◯                                                                        300                                   35     1.9      ◯                                                                           57     ◯                                                                        220                                   36     1.9      ◯                                                                           55     ◯                                                                        300                                   37     1.7      ◯                                                                           60     ◯                                                                        340                                   38     1.9      ◯                                                                           55     ◯                                                                        230                                   39     2.0      ◯                                                                           61     ◯                                                                        300                                   40     1.9      ◯                                                                           60     ◯                                                                        300                                   41     1.8      ◯                                                                           65     ◯                                                                        300                                   42     1.8      ◯                                                                           65     ◯                                                                        200                                   43     1.9      ◯                                                                           60     ◯                                                                        300                                   44     1.8      ◯                                                                           65     ◯                                                                        300                                   45     1.8      ◯                                                                           60     ◯                                                                        305                                   Compar-                                                                       ative                                                                         Example                                                                        1     1.5      X         35     X       10                                    2     0.1      X         35     X       10                                    3     1.5      X         35     X       10                                    4     0.1      X         35     X       10                                   ______________________________________                                    

As seen from Table 2, the amino resin fine powder used in the inventionis excellent in the solubility in the acid or oxidizing agent ascompared with the epoxy resin fine powder used in the comparativeexamples and shows a high peeling strength. Furthermore, the migrationreaction is not observed in the invention.

Thus, according to the invention, not only the high adhesion strength ofthe conductor is obtained, but also the insulation reliability betweenthe conductors is excellent, which are advantageous in the manufactureof high density printed circuit board. Moreover, the surface hardness ishigh and the wire bonding property is excellent, so that the printedcircuit board according to the invention can advantageously be used as asubstrate for mounting bear chip.

The surface resistivity in the adhesive layer is unchangeable ascompared with the initial value even after the adhesive layer isimmersed in a boiling water of 100° C. for 2 hours. Further, there isobserved no abnormal change even after the circuit board is closed to ahot plate of 300° C. and held at this temperature for 10 minutes.

Moreover, the each test method for the adhesion strength (peelingstrength), electrical insulating quality, hardness and impurityinfluence of the electroless plated film is described below.

(1) Adhesion Strength (Peeling Strength)

It was measured according to a method of JIS C-6481.

(2) Electrical Insulating Quality

A direct current or a sine curve alternating current of a frequency of50 Hz or 60 Hz was applied at a peak voltage of 500 V to a comb typepattern of L/S=100/100 μm formed on the printed circuit board. Thevoltage was gradually raised to a given value in about 5 seconds andcharged for 1 minutes, during which mechanical damage, flush over andinsulation breakage (when passing a current of not less than 0.5 mA)were measured.

(3) Hardness (Barcol Hardness)

Device: system A

indication value of aluminum alloy standard piece: 85-87 (hard), 43-48(soft)

Model: GYZJ934-1

Adjustment: hardness was adjusted to a value of 100±1 by using a glassplate and then to the indication value by using the aluminum alloystandard piece.

Operation: an indenting tool of a hardness testing machine wasvertically pushed to a surface of a sample to read a maximum value. Themeasuring position is a smooth surface located inward from the sampleend to not less than 3 mm and separated apart from a recess to not lessthan 3 mm.

Measurement: hardness was measured by heating the substrate at 150° C.and holding this temperature for 5 minutes.

(4) Impurity influence (resistance to migration)

Test piece: printed circuit board having a comb pattern of L/S=50/50 μm

Measurement: the board was placed in a thermo-hygrostat at a temperatureof 85°±1° C. and a relative humidity of 85-90% and left to stand whileapplying a voltage of 30 V. The presence or absence of migration wasmeasured after 1000 hours.

What is claimed is:
 1. An adhesive for a printed circuit board producedby dispersing a cured fine powder of amino resin soluble in an acid oran oxidizing agent into an uncured resin matrix, said uncured resinmatrix being curable into a heat-resistant resin matrix which isinsoluble in an acid or an oxidizing agent.
 2. The adhesive according toclaim 1, wherein said resin matrix having said fine powder of aminoresin dispersed therein is in the form of a layer.
 3. The adhesiveaccording to claim 2, wherein said layer comprises a layer on a basefilm.
 4. The adhesive according to claim 2, wherein said amino resinfine powder is dispersed into said resin matrix in an amount of 10-100parts by weight per 100 parts by weight as a solid content of said resinmatrix.
 5. The adhesive according to claim 2, wherein said amino resinfine powder comprises at least one member selected from the groupconsisting of melamine resins, urea resins and guanamine resins.
 6. Theadhesive according to claim 2, wherein said resin matrix comprises amember selected from the group consisting of thermosettingheat-resistant resins and photosensitive resins.
 7. The adhesiveaccording to claim 2, wherein said resin matrix comprises a mixture of(a) a member selected from the group consisting of uncuredpolyfunctional epoxy resins and uncured difunctional epoxy resins, and(b) an imidazole curing agent.
 8. The adhesive according to claim 7,wherein said resin matrix comprises a mixture of a thermosettingheat-resistant resin comprising 20-100 wt % as a solid content of anuncured polyfunctional epoxy resin, 80-0 wt % of an uncured difunctionalepoxy resin, and 2-10 wt % as a solid content of an imidazole curingagent.
 9. The adhesive according to claim 2, wherein said resin matrixcomprises at least one photosensitive heat-resistant resin selected fromthe group consisting of uncured polyfunctional epoxy resins, uncuredpolyfunctional epoxy resins containing an acryl group and uncuredpolyfunctional acrylic resins.
 10. The adhesive according to claim 9,wherein said resin matrix comprises a mixture of 20-100 wt % as a solidcontent of at least one photosensitive heat-resistant resin selectedfrom the group consisting of uncured polyfunctional epoxy resins,uncured polyfunctional epoxy resins containing an acryl group anduncured polyfunctional acrylic resins, and 80-0 wt % as a solid contentof at least one photosensitive heat-resistant resin selected from thegroup consisting of difunctional epoxy resins and difunctional acrylicresins.
 11. The adhesive according to claim 2, wherein said resin matrixcomprises a mixture (a) of at least one photosensitive heat-resistantresin selected from the group consisting of uncured polyfunctional epoxyresins, uncured polyfunctional epoxy resins containing an acryl groupand uncured polyfunctional acrylic resins, and (b) at least onephotosensitive heat-resistant resin selected from the group consistingof difunctional epoxy resins, and difunctional acrylic resins.
 12. Theadhesive according to claim 11, wherein said resin matrix comprises amixture of 20-100 wt % as a solid content of at least one photosensitiveheat-resistant resin selected from the group consisting of uncuredpolyfunctional epoxy resins, uncured polyfunctional epoxy resinscontaining an acryl group and uncured polyfunctional acrylic resins, and80-0 wt % as a solid content of at least one photosensitiveheat-resistant resin selected from the group consisting of difunctionalepoxy resins, and difunctional acrylic resins.
 13. The adhesiveaccording to claim 2, wherein said amino resin fine powder has anaverage particle size of 0.05-50 μm.
 14. The adhesive according to claim1, wherein said amino resin fine powder is dispersed into said resinmatrix in an amount of 10-100 parts by weight per 100 parts by weight asa solid content of said resin matrix.
 15. The adhesive according toclaim 1, wherein said amino resin fine powder comprises at least onemember selected from the group consisting of melamine resins, urearesins and guanamine resins.
 16. The adhesive according to claim 1,wherein said resin matrix comprises a member selected from the groupconsisting of thermosetting heat-resistant resins and photosensitiveresins.
 17. The adhesive according to claim 1, wherein said resin matrixcomprises a mixture (a) of a member selected from the group consistingof uncured polyfunctional epoxy resins and uncured difunctional epoxyresins, and (b) an imidazole agent.
 18. The adhesive according to claim17, wherein said resin matrix comprises a mixture of a thermosettingheat-resistant resin comprising 20-100 wt % as a solid content of anuncured polyfunctional epoxy resin, 80-0 wt % of an uncured difunctionalepoxy resin, and 2-10 wt % as a solid content of an imidazole curingagent.
 19. The adhesive according to claim 1, wherein said resin matrixcomprises a member selected from the group consisting of:(a) at leastone photosensitive heat-resistant resin selected from the groupconsisting of uncured polyfunctional epoxy resins, uncuredpolyfunctional epoxy resins containing an acryl group and uncuredpolyfunctional acrylic resins; and (b) a mixture of at least onephotosensitive heat-resistant resin selected from the group consistingof uncured polyfunctional epoxy resins, uncured polyfunctional epoxyresins containing an acryl group and uncured polyfunctional acrylicresins, and at least one photosensitive heat-resistant resin selectedfrom the group consisting of difunctional epoxy resins and difunctionalacrylic resins.
 20. An adhesive for a printed circuit board produced bydispersing a cured fine powder of amino resin soluble in an acid or anoxidizing agent into an uncured resin matrix, said uncured resin matrixcomprising a member selected from the group consisting of thermosettingheat-resistant resins and photosensitive resins which is curable into aheat-resistant resin matrix which is insoluble in an acid or anoxidizing agent; and said resin matrix having said fine powder of aminoresin dispersed therein being in the form of a layer on a base film.